diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
index c5793e16a9e890899bd9ae26414961ee9af550a8..256de74d410e4f16de523439f828997fb9d2e2c0 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
@@ -936,6 +936,8 @@ case class AssertNotNull(child: Expression, walkedTypePath: Seq[String] = Nil)
   override def foldable: Boolean = false
   override def nullable: Boolean = false
 
+  override def flatArguments: Iterator[Any] = Iterator(child)
+
   private val errMsg = "Null value appeared in non-nullable field:" +
     walkedTypePath.mkString("\n", "\n", "\n") +
     "If the schema is inferred from a Scala tuple/case class, or a Java bean, " +